In the field of gas turbine engines, the current art is to join a first casing part to a second casing part through an upturned bolted flange. As described below with reference to FIG. 2 and FIG. 3, such a joint is well suited to metallic casing parts, as the metal can easily be formed to create the flanges and the flanges are of metal that is as stiff and strong as the material of the remainder of the casing parts.
However, the present inventors have observed problems with an upturned bolted flange joint, and such problems are discussed below with reference to FIG. 2 and FIG. 3.
In particular, the present inventors have observed that bolted flange loading is also difficult with composite casing parts because the through-thickness loading onto the composite under the bolt head and nut is high. Traditionally, this issue is solved using load spreaders, for example larger and specially shaped washers.
The present invention has been devised in light of the above considerations.
Barrel nuts are a known component for attaching two parts together. Barrel nuts are disclosed, for example, in U.S. Pat. No. 2,789,457, U.S. Pat. No. 4,159,552, and U.S. Pat. No. 3,208,496. Barrel nuts are known for use in assembling flat pack furniture.
U.S. Pat. No. 4,061,073 discloses a crushable collar type bolt fastening similar to current containment flange design philosophy (discussed below with reference to FIG. 2 and FIG. 3).
EP2538035 discloses a joint assembly includes a first component with a flange containing a plurality of spaced through-holes. The joint assembly further includes a second component with a joining portion having an end surface which faces the flange. The joining portion contains a plurality of spaced elongate cavities. Each cavity extends into the joining portion from the end surface in axial alignment with a respective one of the through-holes. The joint assembly further includes a plurality of fixation devices. Each fixation device includes a bolt with a shank which extends through a respective through-hole and the corresponding aligned cavity. Each fixation device further includes a nut which is embedded within the joining portion at the corresponding cavity to threadingly receive the shank such that on tightening the nut and the bolt a clamping force is exerted across the flange and the end surface to join the first and second components together. Each fixation device is configured such that under axial loads less than those causing bolt failure the fixation device is deformable to remove the clamping force across the flange and the end surface.